BMI reading from Monitor vs. standard calculation.

Hi,
Recently had myself measured and logged and from a reportedly accurate electronic BMI device it reported 22.2 which would seem to be a relatively good level, especially since my prior measurement (~6 months ago) reported 26.5
However, online calculators that simply consider height and weight in their calculation is reporting a 25.4
For obvious reasons I would like to believe the device version of my BMI. Can someone explain why the difference? Bone density maybe? Muscle vs fat % ? or simply an unreliable measurement?
From what I can find, the BMI calculation is a pretty straight forward math formula so there must be other factors that are being taken into consideration by the electronic device?

Are you confusing Body Mass Index with body fat percentage? Those are two different calculations, but the numbers for a normal woman end up being similar. Body Mass Index is based off your height and your weight, with a normal range of 20-25. Body fat is an estimate or measurement of how much of your body is composed of fat. This is done in a number of ways (including electronic devices), most of them not being terribly accurate. Normal for a woman is also about 20-25% or so, but for men, a normal number is closer to 10-12%.

BMI is useful for trending across populations, but quickly breaks down on an individual level. Bodyfat is far more relevant for an individual, but harder to measure/calculate properly. Different methods will give you wildly different answers.

TL;DR: Don't trust the device. Don't rely on the BMI. Log one or both over time to see trends, but don't trust them as absolute numbers. An individual measurement of either is not going to tell you what you want to know.

Yeah, I can now agree. BMI would seem too general to mean anything.
So yep, the measurement was my body fat %
While as of end of last month I was at 22.6% which was a bit higher then I was hoping (though now that I take a good look at myself it's sort obvious). But on the bright side, my measurement from 6 months back wasn't 26.5%, it was 29.5% and have a goal of 17% by September so it would appear I'm tracking pretty well to this.